NGUI对象跟随鼠标拖拽移动

public Camera WNGUICamera;    Vector3 _WoldPosition;//指针的初始位置    // Vector3 _WoldAng;    Vector3 WscreenSpace;    Vector3 Woffset;    Vector3 WcurScreenSpace;    Vector3 WcurPosition;      //工具跟随鼠标拖拽移动    IEnumerator fnOnMouseDown()    {        WscreenSpace = WNGUICamera.WorldToScreenPoint(transform.position);        Woffset = transform.position - WNGUICamera.ScreenToWorldPoint(new Vector3(Input.mousePosition.x,Input.mousePosition.y, WscreenSpace.z));        while (Input.GetMouseButton(0))        {            //DrawLineScript.isMoveLine = true;            if (Input.mousePosition.x > 0 && Input.mousePosition.x < Screen.width && Input.mousePosition.y > 0 && Input.mousePosition.y < Screen.height)            {                WcurScreenSpace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, WscreenSpace.z);                WcurPosition = WNGUICamera.ScreenToWorldPoint(WcurScreenSpace) + Woffset;                transform.position = new Vector3(WcurPosition.x, WcurPosition.y, 0f);            }            yield return new WaitForFixedUpdate();        }    }